Transmissions typically include a series of gear meshes for establishing different power paths through the transmission. To facilitate shifting from one power path to another, such transmissions are provided with synchronizer assemblies.
A conventional synchronizer assembly includes a synchronizer hub which is connected for rotation to a transmission shaft journalled within a transmission housing. A synchronizer ring is fit between the synchronizer hub and a clutch ring which engages with a gear forming part of a gear mesh. Depending upon the particular synchronizer assembly design, it is conventional to provide synchronizer and clutch rings on opposite sides of the synchronizer hub for engagement with gears forming part of first and second gear meshes. The synchronizer assembly further includes a sliding sleeve whose position is controlled by the operator as with a shifting collar. As is well known in the art, the sliding sleeve acts to couple the synchronizer hub to the clutch ring through the synchronizer ring as by a dog clutch type connection.
The clutch ring and the synchronizer ring each have generally corresponding frusto-conical interfacing surfaces therebetween. Interengagement between the frusto-conical surfaces on the rings tends to synchronize the speed of the synchronizer hub with the clutch ring thus facilitating engagement of the dog clutch connection and thereby effecting smooth engagement of the gear mesh.
The synchronizer assembly is designed to operate in an efficient and smooth manner when accurate and proper operating clearances are provided between inter-engaging parts of the synchronizer assembly. As will be appreciated by those skilled in the art, a predetermined tolerance is required between the parts of the synchronizer to allow the synchronizer assembly to operate in a neutral band or mode. There are specific tolerances between the parts depending upon the frictional material used to fabricate the synchronizer assembly. Moreover, tolerances are required between the respective gears and synchronizer hub to establish a running clearance therebetween. A proper clearance is furthermore required between the synchronizer hub and the gear such that proper lubrication is provided to the parts of the synchronizer assembly. As will be appreciated, too much lubricant can be detrimental to operation of the synchronizer assembly. Conversely, too little lubricant can likewise be detrimental to the proper operation of the synchronizer assembly.
The ability to properly set clearances for the synchronizer assembly may further be complicated by the transmission design. In some transmission designs, one end of the shaft on which the synchronizer assembly is mounted includes a gear which intermeshes with a pinion gear. Endwise positioning of the shaft is often required to provide a proper backlash setting between the gears. As will be appreciated, endwise shifting of the shaft complicates the ability to set proper clearances for the synchronizer assembly and, thus, effects performance and proper lubrication of the synchronizer assembly. Some transmissions used on off-highway equipment often include two axially aligned shafts which extend through different transmission compartments and are typically spline connected to each other at their ends. The tolerances involved with two axially aligned shafts arranged in driving relation relative to each other further complicates the ability to properly set clearances for the synchronizer assembly.
A conventional synchronizer assembly may have as many as seven different areas wherein manufacturing tolerances complicate the ability to set a proper and accurate working clearance for the synchronizer assembly. A conventional approach to solving the problem involves providing a snap-ting at opposite ends of the synchronizer assembly to control tolerance stackups. This approach, however, complicates the transmission design and can add substantial costs to the manufacturing process. The design of the gears and related parts do not always lend themselves to use of a standard or conventional synchronizer assembly. Thus, specifically sized parts need to be manufactured and snap-ting grooves need to be provided in the shafts to absorb the tolerances involved in such unique arrangements. Moreover, it is difficult to evaluate and access the tolerance stackup between the parts as the transmissions is assembled and, thus, a laborious process involving tear down and build up of the transmission is required to accomplish the accurate and proper clearances for the components of the synchronizer assembly.
Thus, there is a need and a desire for an apparatus arranged in combination with a transmission synchronizer assembly which provides accurate operating clearances for the synchronizer assembly notwithstanding the tolerance stackup of the inter-related parts and in a manner eliminating the need to tear down and reassemble the transmission to accomplish the operating clearances between the inter-related parts.